Blue whales mostly emit very loud, highly structured, repetitive low-frequency rumbling sounds that can travel for many miles underwater. These songs may be used for communicating with other blue whales, especially in order to attract and find mates.

The call of the blue whale reaches levels up to 188 decibels. This extraordinarily loud whistle can be heard for hundreds of miles underwater. Theoretical calculations by Roger Payne and Douglas Webb (from the 1970's) predicted that the loudest whale sounds might be transmitted across an entire ocean. The blue whale is much louder than a jet, which reaches only 140 decibels! Human shouting is 70 decibels; sounds over 120 decibels are painful to human ears. The second-loudest animal on Earth is the howler monkey (Alouatta) from the jungles of Central and South America.

PRODUCING VOCALIZATIONS
The source of whale sound production is unknown, but the larynx is the likely source. Unlike humans, whales have no vocal cords in their larynx. Whales produce sounds two ways: by moving air through a tubed extension of the larynx to the nasal plugs (located near the nasal sacs near the blowhole). P.E. Purves (1967) suggested that whale sounds are mostly produced in the larynx region and the nasal sacs, as air is moved between nasal sacs. K.S. Norris et al. (1971) suggested that whale whistles are produced in the nasal plugs.